This invention relates to a method for providing audio, video and/or data communication services, in real-time, to a multiplicity of users on a communications network, such as the Internet.
Systems such as the Internet typically are point-to-point, or unicast, systems in which a message is converted into a series of addressed packets that are routed from a source node through a plurality of routers to a destination node. In most communication protocols the packet includes a header which contains the addresses of the source and the destination nodes as well as a sequence number which specifies the packet""s order in the message. Although the Internet was initially used in this manner almost exclusively, it is now also used for multicasting, where many points transmit, and each transmitting point transmits to many points. Conferencing is one example where multicasting is found to be useful. To satisfy such demands, packets destined for several recipients are sometimes encapsulated in a unicast packet and forwarded from a source to a point in a network where the packets are replicated and forwarded on to all desired recipients. This technique is known as IP Multicasting and the network over which such packets are routed is referred to as the Multicast Backbone, or MBONE. More recently, routers have become available which can route the multicast addresses (class D addresses) provided for in communication protocols such as TCP/IP and UDP/IP. A multicast address is essentially an address for a group of host computers who have indicated their desire to participate in that group. Thus, a multicast packet can be routed from a source node through a plurality of multicast routers (or mrouters) to one or more devices receiving the multicast packets. From there the packet is distributed to all the host computers that are members of the multicast group.
These techniques have been used to provide on the Internet audio and video conferencing as well as radio-like broadcasting to groups of interested parties. See, for example, K. Savetz et al. MBONE Multicasting Tomorrow""s Internet (IDG Books WorldWide Inc., 1996). Other details concerning technical aspects of multicasting may be found in the Internet documents Request for Comments (RFC) 1112 and, and in D. P. Brutaman et al., xe2x80x9cMBONE provides Audio and Video Across the Internet,xe2x80x9d IEEE Computer, Vol. 27, No. 4, pp. 30-36 (April 1994).
Indeed, there is now a great deal of music and other audio and video content that is being transmitted over the Internet as multicast transmissions. This situation will, no doubt, lead to the kind of channel surfing that viewers engage in with their home TVs. However, unlike the situation with home TVs, car radios, and the like, switching between multicasting channels on the internet is not straight forward, in that when switching to a new channel, buffering and routing operations must be done which cause a several second delay in receiving the content of the newly selected channel. This makes the surfing unsatisfactory because it is much slower than what people are used to.
The above-mentioned deficiency is overcome, in accordance with the principles disclosed herein, with an arrangement where a user receives a number of channels concurrently. The channel that is of current interest to the user is sent with a given bandwidth, while other channels (surfing channels) are sent at reduced bandwidth. The user""s receiver buffers all of the received channels, and plays the channel of current interest in full fidelity. When a user wishes to surf, the buffered surfing channels are made available and are played to the user in accordance with the user""s requests. When the user selects another channel to be of current interest, the user""s terminal sends out a request for the new channel to be sent to the user at the given bandwidth, and thence provides the user with the newly selected channel at full fidelity.